1. Field of the Invention
The present invention relates generally to methods for fabricating magnetic sensor elements. More particularly, the present invention relates to methods for fabricating non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor elements.
2. Description of the Related Art
The recent and continuing advances in computer and information technology have been made possible not only by the correlating advances in the functionality, reliability and speed of semiconductor integrated circuits, but also by the correlating advances in the storage density and reliability of direct access storage devices (DASDs) employed in digitally encoded magnetic data storage and retrieval.
Storage density of direct access storage devices (DASDs) is typically determined as areal storage density of a magnetic data storage medium formed upon a rotating magnetic data storage disk within a direct access storage device (DASD) magnetic data storage enclosure. The areal storage density of the magnetic data storage medium is defined largely by the track width, the track spacing and the linear magnetic domain density within the magnetic data storage medium. The track width, the track spacing and the linear magnetic domain density within the magnetic data storage medium are in turn determined by several principal factors, including but not limited to: (1) the magnetic read-write characteristics of a magnetic read-write head employed in reading and writing digitally encoded magnetic data from and into the magnetic data storage medium; (2) the magnetic domain characteristics of the magnetic data storage medium; and (3) the separation distance of the magnetic read-write head from the magnetic data storage medium.
With regard to the magnetic read-write characteristics of magnetic read-write heads employed in reading and writing digitally encoded magnetic data from and into a magnetic data storage medium, it is known in the art of magnetic read-write head fabrication that magnetoresistive (MR) sensor elements employed within magnetoresistive (MR) read-write heads are generally superior to other types of magnetic sensor elements when employed in retrieving digitally encoded magnetic data from a magnetic data storage medium. In that regard, magnetoresistive (MR) sensor elements are generally regarded as superior since magnetoresistive (MR) sensor elements are known in the art to provide high output digital read signal amplitudes, with good linear resolution, independent of the relative velocity of a magnetic data storage medium with respect to a magnetoresistive (MR) read-write head having the magnetoresistive (MR) sensor element incorporated therein.
Within the general category of magnetoresistive (MR) sensor elements, magnetoresistive (MR) sensor elements which employ multiple magnetoresistive (MR) layers (typically including a pair of magnetoresistive (MR) layers), such as but not limited to dual stripe magnetoresistive (DSMR) sensor elements and spin valve magnetoresistive (DSVMR) sensor elements, and in particular magnetoresistive (MR) sensor elements which employ multiple magnetoresistive (MR) layers at least one of which is magnetically biased to provide non-parallel magnetic bias directions of the multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor elements, such as nominally anti-parallel longitudinally magnetically biased dual stripe magnetoresistive (DSMR) sensor elements and nominally perpendicularly magnetically biased spin valve magnetoresistive (DSVMR) sensor elements, are presently of considerable interest insofar as the magnetically biased magnetoresistive (MR) layers employed within such magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor elements typically provide enhanced magnetic read signal amplitude and fidelity in comparison with single stripe magnetoresistive (MR) sensor elements, non-magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor elements and parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor elements.
While non-parallel magnetically biased multiple magnetoresistive (R) layer magnetoresistive (MR) sensor elements such as but not limited to non-parallel longitudinally magnetically biased dual stripe magnetoresistive (DSMR) sensor elements and non-parallel perpendicularly magnetically biased dual spin valve magnetoresistive (DSVMR) sensor elements are thus desirable within the art of digitally encoded magnetic data storage and retrieval, non-parallel multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor elements are nonetheless not fabricated entirely without problems in the art of magnetoresistive (MR) sensor element fabrication. In particular, as a data track width within a magnetic medium employed within digitally encoded magnetic data storage and retrieval decreases, it becomes increasingly important that a read track width within a non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element employed in reading the data within the data track be uniformly magnetically biased (i.e. have a uniform cross-track magnetic bias profile). Uniform cross-track magnetic bias profiles are desirable within read track widths of non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor elements since such uniform cross-track magnetic bias profiles provide for optimal magnetic read signal amplitudes within such non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor elements.
It is thus towards the goal of providing, for use within magnetic data storage and retrieval, a method for forming a non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element with a uniform cross-track magnetic bias profile across a read track width of the non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element, as well as a non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element formed in accord with the method, that the present invention is most generally directed.
Various methods and resultant magnetoresistive (MR) sensor element structures have been disclosed in the art of magnetoresistive (MR) sensor element fabrication for forming magnetically biased magnetoresistive (MR) sensor elements with enhanced functionality, enhanced reliability or other desirable properties.
For example, Voegeli et al., in U.S. Pat. No. 5,561,896, discloses a method for fabricating, with enhanced longitudinal magnetic bias characteristics, enhanced fabrication simplicity and enhanced reliability, a longitudinally magnetically biased magnetoresistive (MR) sensor element for use within magnetic data storage and retrieval. The method employs an xe2x80x9cHxe2x80x9d shaped laminate formed of a soft magnetoresistive (MR) material layer laminated to an interdiffusion material layer, where upon thermally induced interdiffusion of the soft magnetoresistive (MR) material layer and the interdiffusion material layer there is formed a hard magnetic bias material layer therefrom, and where interdiffusion of the soft magnetoresistive (MR) material layer with the interdiffusion material layer is effected by an electrical pulsing through a pair of leg portions of the xe2x80x9cHxe2x80x9d but not a horizontal connector portion of the xe2x80x9cHxe2x80x9d, such that the pair of leg portions of the xe2x80x9cHxe2x80x9d is transformed into a pair of hard magnetic bias material layers while the horizontal connector portion of the xe2x80x9cHxe2x80x9d remains un-interdiffused as the soft magnetoresistive (MR) material layer which is longitudinally magnetically biased by the pair of hard bias magnetic bias material layers formed from the thermally interdiffused leg portions of the xe2x80x9cHxe2x80x9d.
In addition, Dovek et al., in U.S. Pat. No. 5,650,887, discloses a system for retrieving magnetic data from a magnetic data storage medium while employing a spin valve magnetoresistive (SVMR) sensor element, and a disk drive magnetic data storage enclosure which employs the system for retrieving the magnetic data from the magnetic data storage medium while employing the spin valve magnetoresistive (SVMR) sensor element, where the spin-valve magnetoresistive (SVMR) sensor element may be readily reset to its original magnetic orientation subsequent to an event which dislocates within the spin valve magnetoresistive (SVMR) sensor element a magnetic exchange bias pinned layer from its original magnetic orientation within the spin-valve magnetoresistive (SVMR) sensor element. To achieve the foregoing result, the system employs: (1) an electrical current waveform directed through the spin-valve magnetoresistive (SVMR) sensor element with an initial current sufficient to heat a magnetic exchange bias pinning layer within the spin-valve magnetoresistive (SVMR) sensor element above its blocking temperature; and (2) a subsequent lower current sufficient to generate a magnetic field around the magnetic exchange bias pinned layer pinned by the magnetic exchange bias pinning layer to properly magnetically orient the magnetic exchange bias pinned layer while the magnetic exchange bias pinning layer is cooling below its blocking temperature.
Further, Shi et al., in U.S. Pat. No. 5,684,658, discloses a dual stripe magnetoresistive (DSMR) sensor element and a method for fabricating the dual stripe magnetoresistive (DSMR) sensor element, where the dual stripe magnetoresistive (DSMR) sensor element has a narrow read back width which in turn provides that the narrow read back width dual stripe magnetoresistive (DSMR) sensor element may be employed for reading digitally encoded magnetic data within narrowly spaced tracks within a magnetic data storage medium. The dual stripe magnetoresistive (DSMR) sensor element realizes the foregoing object by employing when forming the dual stripe magnetoresistive (DSMR) sensor element: (1) an offset of a first magnetoresistive (MR) layer with respect to a second magnetoresistive (MR) layer within the dual stripe magnetoresistive (DSMR) sensor element; (2) a parallel longitudinal magnetic biasing of the first magnetoresistive (MR) layer with respect to the second magnetoresistive (MR) layer within the dual stripe magnetoresistive (DSMR) sensor element; and (3) an anti-parallel electromagnetic biasing of the first magnetoresistive (MR) layer with respect to the second magnetoresistive (MR) layer within the dual stripe magnetoresistive (DSMR) sensor element.
Still further, Han et al., in U.S. Pat. No. 5,783,460, discloses a method for fabricating a dual stripe magnetoresistive (DSMR) sensor element, where there is minimized tolerance variations with respect to the width and/or alignment between a pair of magnetoresistive (MR) layers within the dual stripe magnetoresistive (DSMR) sensor element. To realize the foregoing object, the method employs a lift off stencil as an etch mask for forming from a trilayer blanket stack layer comprising: (1) a blanket first magnetoresistive (MR) layer having formed thereupon; (2) a blanket inter-stripe dielectric layer, in turn having formed thereupon; (3) a blanket second magnetoresistive (MR) layer, a corresponding trilayer patterned stack layer comprising: (1) patterned first magnetoresistive (MR) layer having formed thereupon; (2) a patterned inter-stripe dielectric layer in turn having formed thereupon; (3) a patterned second magnetoresistive (MR) layer, wherein the series of three foregoing patterned layers within the trilayer patterned stack layer in turn has a series of fully aligned edges.
Finally, Ohtsuka et al., in U.S. Pat. No. 5,859,753, discloses a spin-valve magnetoresistive (SVMR) sensor element, and a method for fabricating the spin-valve magnetoresistive (SVMR) sensor element, where the spin-valve magnetoresistive (SVMR) sensor element has an attenuated susceptibility to thermal asperities and electrostatic discharge when employing the spin-valve magnetoresistive (SVMR) sensor element for retrieving magnetic data from a magnetic data storage medium. The spin-valve magnetoresistive (SVMR) sensor element realizes the foregoing objects by employing a dual spin-valve magnetoresistive (DSVMR) sensor element construction wherein: (1) a pair of pinned magnetoresistive layers within the dual spin-valve magnetoresistive (DSVMR) sensor element is magnetically pinned in opposite directions; and (2) one conductor lead layer within each pair of conductor lead layers employed within the dual spin-valve magnetoresistive (DSVMR) sensor element construction is positioned with respect to the magnetic data storage medium from which is retrieved magnetic data further removed than the other conductor lead layer within the pair of conductor lead layers.
Desirable within the art of non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element fabrication are additional methods and materials which may be employed for forming non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor elements with enhanced magnetic bias profile uniformity of the non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor elements within the trackwidths of the non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor elements.
It is towards the foregoing object that the present invention is directed.
A first object of the present invention is to provide a non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element, and a method for fabricating the non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element, where the non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element has an enhanced magnetic bias profile uniformity within a trackwidth of the non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element.
A second object of the present invention is to provide a non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element and a method for fabricating the non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element in accord with the first object of the present invention, which method is readily commercially implemented.
In accord with the objects of the present invention, there is provided by the present invention a method for fabricating a non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element. To practice the method of the present invention, there is first provided a substrate. There is then formed over the substrate a first magnetoresistive (NM) layer. There is also formed contacting the first magnetoresistive (MR) layer a magnetically biased first magnetic bias layer, where the magnetically biased first magnetic bias layer is biased in a first magnetic bias direction with a first magnetic bias field strength. There is also formed separated from the first magnetoresistive (MR) layer by a spacer layer a second magnetoresistive (MR) layer. There is also formed contacting the second magnetoresistive (MR) layer a magnetically un-biased second magnetic bias layer. There is then biased through use of a first thermal annealing method employing a first thermal annealing temperature, a first thermal annealing exposure time and a first extrinsic magnetic bias field strength the magnetically un-biased second magnetic bias layer to form a magnetically biased second magnetic bias layer having a second magnetic bias field strength in a second magnetic bias direction non-parallel to the first magnetic bias direction while simultaneously partially demagnetizing the magnetically biased first magnetic bias layer to form a partially demagnetized magnetically biased first magnetic bias layer having a partially demagnetized first magnetic bias field strength less than the first magnetic bias field strength. Finally, there is then annealed thermally through use of a second thermal annealing employing a second thermal annealing temperature and a second thermal annealing exposure time without a second magnetic bias field: (1) the partially demagnetized magnetically biased first magnetic bias layer to form a remagnetized partially demagnetized first magnetic bias layer having a remagnetized partially demagnetized first magnetic bias field strength greater than the partially demagnetized first magnetic bias field strength; and (2) the magnetically biased second magnetic bias layer to form a further magnetically biased second magnetic bias layer having a further magnetized second magnetic bias field strength greater than the second magnetic bias field strength.
Advantageously, the method of the present invention provides that: (1) a first magnetic bias layer from which is formed the magnetically biased first magnetic bias layer; and (2) the second magnetic bias layer, may both be formed from a single magnetic bias material. Thus, use of such a single magnetic bias material assists in optimizing a cross-track magnetic bias profile uniformity of a non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element. To the extent not previously disclosed or claimed within the art of magnetoresistive (MR) sensor element fabrication, the present invention also contemplates various non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor elements formed employing multiple non-parallel magnetically biased magnetic bias layers formed of a single magnetic bias material.
The present invention provides a non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element, and a method for fabricating the non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element, where the non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element has an enhanced magnetic bias profile uniformity within a trackwidth of the non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element. The method of the present invention realizes the foregoing object by employing when fabricating the non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element: (1) a first thermal annealing method employing a first thermal annealing temperature, a first thermal annealing exposure time and a first extrinsic magnetic bias field strength to form from a magnetically un-biased second magnetic bias layer a magnetically biased second magnetic bias layer having a second magnetic bias field strength in a second magnetic bias direction non-parallel to a first magnetic bias direction of a magnetically biased first magnetic bias layer, while simultaneously partially demagnetizing the magnetically biased first magnetic bias layer to provide a partially demagnetized magnetically biased first magnetic bias layer having a partially demagnetized first magnetic bias field strength less than a first magnetic bias field strength; and (2) a second thermal annealing method employing a second thermal annealing temperature and a second thermal annealing exposure time without a second magnetic bias field: (a) to form from the partially demagnetized magnetically biased first magnetic bias layer a remagnetized partially demagnetized first magnetic bias layer having a remagnetized partially demagnetized first magnetic bias field strength greater than the partially demagnetized first magnetic bias field strength; and (b) to form from the magnetically biased second magnetic bias layer a further magnetically biased second magnetic bias layer having a further magnetized second magnetic bias field strength greater than the second magnetic bias field strength.
The method of the present invention is readily commercially implemented. The method of the present invention employs thermal annealing methods which are generally known in the art of magnetoresistive (MR) sensor element fabrication. Since it is a process control within the present invention which provides at least in part the method of the present invention, rather than the existence of methods and materials which provides the present invention, the method of the present invention is readily commercially implemented.